Photographic images

ABSTRACT

The production of an improved image by first producing an imagewise metallic silver image in a photosensitive layer and then treating the layer with a substance which decomposes at the metallic silver to result in a superimposed vesicle image. The vesicle image increases the density of the original silver image to provide high sharpness. The process is carried out using a silver salt emulsion in a binding agent to provide the metallic silver upon photographic processing. The binding agent is a suitable resin.

United States Patent Edith Weyde Kuerten, Germany Dec. 12, 1968 Oct. 26, 1971 AGFA-Gevaert Aktiengesellschatt Leverkusen, Germany Dec. 23, 1967 Germany Inventor Appl. No. Filed Patented Assignee Priority PHOTOGRAPHIC IMAGES 5 Claims, No Drawings u.s. c1 96/50, 96/27, 96/48, 96/88, 96/1 19 rm.c1 603C 5/26, G03c 5/00 Field of Search 96/48, 50, 60, 63. 27, as, 119

Primary Examiner-William D. Martin Assistant ExaminerBenard D. Pianalto Attorney-Connolly and Hutz ABSTRACT: The production of an improved image by first producing an imagewise metallic silver image in a photosensitive layer and then treating the layer with a substance which decomposes at the metallic silver to result in a superimposed vesicle image. The vesicle image increases the density of the original silver image to provide high sharpness. The process is carried out using a silver salt emulsion in a binding agent to provide the metallic silver upon photographic processing. The binding agent is a suitable resin.

PHOTOGRAPHIC IMAGES This invention relates to photographic images which consist of a silver image and a vesicle image superimposed on the silver image, and processes for producing these images.

The production of vesicular images comprises light-scattering photographic materials containing a supported or self-supported layer having photolytic compounds dispersed therein, which upon exposure and development by that treatment yields minute vesicles acting as light-scattering centers. The unexposed areas of the layer remain transparent. The vesicular image therefore appears dark in transmitted light but pale when viewed in reflected light. The main disadvantage of vesicular photography is the low light sensitivity of the photographic compounds.

It is among the objects of the invention to provide a process for the production of vesicular images by utilizing light-sensitive layers with increased photographic speed.

We have found that photographic images can be produced by treating imagewise distributed silver which has been produced in accordancewith common photographic practice with a compound which is decomposed by the silver image with formation of gas, the'gas expanding upon heat treatment to form a vesicular image. Photographic images are obtained which consist of metallic silver and an image of minute vesicles superimposed on the silver image.

The inventive process is highly advantageous since silver salt emulsion layers, especially silver halide emulsion layers, of relatively high light sensitivity can be used for the production of the images. n the other hand the invention provides a greater density of the silver images produced in the photographic silver salt layers by the superimposition of the vesicular image. It is therefore possible to start with layers of a relatively low silver halide content for carrying out the process and then to increase the density of the silver images produced in the layers to images of desired density by the superimposition of a vesicular image. Images of high density can be obtained using light-sensitive silver salt emulsion layers, especially silver halide gelatin emulsion layers, which have a silver content of only about 0.2 g. of silver per square meter. Apart from the fact that a considerable saving in silver is achieved by this process, the combined silver and vesicular images have a great advantage in that they have exceptionally high sharpness. The process is particularly advantageous for the production of microfilm and X-ray images.

The process is carried out using silver halide emulsion layers the binding agent of which is suitable for the production of bubble images. Suitable binding agents are synthetic or natural film-forming resins or mixtures thereof.

The light-sensitive silver halide emulsion layers are processed according to common practice including the steps of imagewise exposure, photographic development and fixing to remove the unexposed silver halide. The resulting silver images which may be hardly visible are brought into contact, for example, with hydrogen peroxide (H 0 The hydrogen peroxide may either act on the silver image as a gas or be introduced into the layer is solution. If the layer is heated with hydrogen peroxide during or after this treatment, a vesicular image is formed in the areas of the silver image. The density of the vesicular image depends on the quantity of hydrogen peroxide used, the quantity of silver and the thickness of the layer in which the silver image is produced. The heat treatment of the material to produce the light-scattering vesicles should be carried out immediately after or simultaneously with the treatment with hydrogen peroxide. The temperature which is used for this heat treatment depends on the properties of the binding agent. Satisfactory results can be obtained at relatively low temperatures, such as 60 to 70 C., but higher temperatures can also be used. If gelatin is used as binder, it is advisable to operate in the presence of limited quantities of water because this promotes swelling of the gelatin an hence vesicle formation.

The inventive process represents a combination of the conventional silver halide photography and a vesicular process,

whereby not only an increased speed of the vesicular process is obtained but also a relative increase of the light sensitivity of the silver halide emulsion layer. Due to the high catalytic action of silver or silver oxide on the decomposition of hydrogen peroxide even invisible traces of silver effect the formation of minute vesicles. In other words parts of the image become visible which would remain invisible if processed only according to conventional processing of exposed silver halide emulsion layers. The relative gain in sensitivity lies between 5 and 10 DIN.

For instance a low sensitive fine-grained silver halide emulsion layer which upon conventional processing has a sensitivity of about 13 DIN, can be exposed as an emulsion with a sensitivity of 18 DlN if processed according to the present invention without any loss of details or density in the resulting image.

According to a preferred embodiment of the inventive process the exposed and conventionally processed silver halide emulsion layer is first treated with vapor of hydrogen peroxide and thereafter subjected to water vapor of a temperature of about 50-90 C. for about l-5 seconds. Upon treatment with water vapor the light-scattering minute vesicles are promptly formed.

It is particularly advantageous to subject the processed silver halide layer which was treated with hydrogen peroxide to alkaline water vapor at a pH of between about 8 and 12. This is easily achieved by adding to the water vapor minor amounts of ammonia or vapors of volatile amines. The concentration of the alkaline additives is not critical. Generally amounts between 0.1-5 particularly 0.3-1 percent per volume based on the volume of the water vapor having proved sufficient.

EXAMPLE 1 EXAMPLE 2 A photographic silver image obtained as described in example l, but in this case with a density of 0.4, is dipped for a few seconds into ethyl alcohol which contains l percent by weight of hydrogen peroxide, and which has a temperature of C. When using highly hardened gelatin emulsion layers, it is advisable to add about 1 percent by weight of water to this solution. The final image consisting of silver and light-scattering minute vesicles has a density of 1.8.

EXAMPLE 3 A light-sensitive photographic material including a silver iodobromide gelatin emulsion layer (3.5 mol percent of silver iodide based on the total amount of silver halide) which has a sensitivity of 17 DlN as related to conventional processing is exposed as a photographic material which would have a sensitivity of 25 DlN.

It is developed in a developer of the following composition:

3g. lg.

hydroquinone p-methylaminophenol sodium sulfite l3 g. sodium carbonate 26 g. potassium bromide water up to l liter The developed material is fixed in a conventional aqueous bath of sodium thiosulfate.

The negative silver image of the original is obtained, which is scarcely visible and which is not capable of being copied by conventional photographic processes.

A further processing is performed as follows:

1. Treatment with saturated hydrogen peroxide vapor for 30 seconds at a temperature of 70 C.;

2. subjected to water vapor for 3 seconds at a temperature of 75 C.

Promptly upon treatment with water vapor a very high increase of density occurs. An image portion which has, for example, a density of 0.3 in the fixed negative is intensified to a density of 1.9 by the inventive processing.

If the water vapor applied in step 2 additionally contains 0.5 percent by volume of ammonia, the increase in density is even higher. Image portions which had a density of 0.3 show for example a density of 2.3 after the intensification. In the case of the ammoniacal water vapor the treatment time is reduced to some fractions of a second.

Both negatives, the density of which is increased in accordance with the inventive process, can be copied in accordance with common practice in contact or by means of an enlarging device. Copies of normal contrast are obtained.

I claim:

1. A photographic material comprising a layer having a binding agent selected from the group consisting of synthetic or natural film-forming binding agents or mixtures thereof, and having an image of metallic silver produced by imagewise exposure, development and fixing of the silver salt emulsion, and containing minute vesicles produced by decomposition of an unstable gas-forming compound under the catalytic action of said metallic silver.

2. A process for the production of photographic images consisting of silver and minute vesicles superimposed on the silver in a binder layer including the steps of l. imagewise exposing a layer of a binding agent selected from the group consisting of synthetic or forming binding agents or mixtures thereof and a light-sensitive silver salt and developing the exposed layer to form a metallic silver image therein;

2. treating the said layer containing the silver image with hydrogen peroxide which is decomposed by the silver image to form a gas or a product which is volatile upon heating of the layer and 3. heating said layer and decomposing said hydrogen peroxide to form light scattering vesicles in accordance with the silver image.

3. The process of claim 2, wherein the silver image is treated with vapor of hydrogen peroxide and thereafter with water vapor at a temperature of between 5090 C.

4. The process of claim 3, wherein the treatment with water vapor is performed at a pH of between 8 and 12.

5. The process of claim 3, wherein the water vapor in addition contains 0.1-5 percent by volume of ammonia.

t t 3 I i 

2. A process for the production of photographic images consisting of silver and minute vesicles superimposed on the silver in a binder layer including the steps of
 2. treating the said layer containing the silver image with hydrogen peroxide which is decomposed by the silver image to form a gas or a product which is volatile upon heating of the layer and
 3. heating said layer and decomposing said hydrogen peroxide to form light scattering vesicles in accordance with the silver image.
 3. The process of claim 2, wherein the silver image is treated with vapor of hydrogen peroxide and thereafter with water vapor at a temperature of between 50* - 90* C.
 4. The process of claim 3, wherein the treatment with water vapor is performed at a pH of between 8 and
 12. 5. The process of claim 3, wherein the water vapor in addition contaIns 0.1- 5 percent by volume of ammonia. 